Re: [CFT]: ClangBSD is selfhosting, we need testers now

Andrew Reilly schrieb am 2010-04-22:
> On Wed, Apr 21, 2010 at 05:23:38PM +0200, Roman Divacky wrote:
> > On Wed, Apr 21, 2010 at 05:20:57PM +0200, Alexander Best wrote:
> > > i might have stumbled upon a problem with clang. i've compiled a
> > > kernel from
> > > the clang branch using `make kernel INSTKERNNAME=clang` and
> > > booted from it.
> > > i'm now experiencing audio problems with mp3s and certain video
> > > files.
> > > playback is awfully slow and the audio output gets distorted
> > > massively. `top`
> > > however reports no high cpu load and `vmstat -i` doesn't report
> > > anything
> > > unusual either.

> > > this problem doesn't occur with a regular gcc-kernel.

> > > both kernels are running under a regular (gcc) world.

> > > i thought it might be a problem with acpi, but disabling acpi
> > > (hint.acpi.0.disabled=1) gives me a system freeze.

> > I've heard about this problem but did not manage to reproduce that.

> > can you try to bisect what file is being miscompiled? ie. compile
> > half of the kernel with gcc and half with clang and bisect this
> > way to a single file.

> The FreeBSD sound subsystem has a sample-rate converter built
> into the feeder that (from a cursory look) is probably quite
> carefully tweaked to be able to perform well (or at all).  I've
> added -multimedia to the CC line, because they're the guys
> who are going to know the details.  It's possible that some
> GCC-specific manifest constants are being tested-for, with
> sub-optimal fall-back code being run, instead.

> In the mean-time, Alexander, are there any sound-related sysctls
> that you can tweak so that the audio playback that you're doing
> does *not* involve sample rate conversion?

i'm not sure because i'm not an expert on audio stuff. these sysctl vars might
contain the functionality you mentioned:

hw.snd.feeder_rate_presets: 100:8:0.85 100:36:0.92 100:164:0.97
hw.snd.feeder_rate_polyphase_max: 183040
hw.snd.feeder_rate_min: 1
hw.snd.feeder_rate_max: 2016000
hw.snd.feeder_rate_round: 25
hw.snd.feeder_rate_quality: 1
hw.snd.feeder_eq_presets:
PEQ:16000,0.2500,62,0.2500:-9,9,1.0:44100,48000,88200,96000,176400,192000
hw.snd.feeder_eq_exact_rate: 0


> Cheers,


-- 
Alexander Best